buddypoor
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hello RAJ,
What you are saying there is sufficent condition for the sustained oscilation. What i feel is if you have gain>1, then it start increasing with time [i](exponentially this is what i mean blowing) and if you have sufficient non-linerity in the ckt then it will be oscilate[/i].
No, that`s not the case. Although most of the circuits with loop gain T(s)=1 will behave like this, there are exceptions as given by me as counterexamples. Thus, this criterion is NOT sufficient. For example, the WIEN circuit with opamp inputs exchanged needs a RISING gain for rising amplitudes in order to bring the eigenvalue back to the LHP of the s-plane (stabilizatuion). But that is contradictory.
Coming to your example WIEN oscillator with exachanged opamp inputs, it can't oscilate because there is no DC -ve feedback, how it will get bised? That`s the reason I mentioned the IDEAL opamp that needs no dc bias. Nevertheless, it will not oscillate.
Finally, believe me, up to now there is no sufficient oscillation criterion. If you have the opportunity to read "Analog Integrated Circuits and signal processing" you will find some recently published articles dealing with this subject. Regards buddypoor
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